What's the difference between an exclusive lock and a shared lock?

Question

According to wikipedia,

Shared locks are sometimes called \"read locks\" and exclusive locks are sometimes called \"write locks\".

Answer 1

• An exclusive or write lock gives a process exclusive access for writing to the specified part of the file. While a write lock is in place, no other process can lock that part of the file.

• A shared or read lock prohibits any other process from requesting a write lock on the specified part of the file. However, other processes can request read locks.

More on that : http://www.gnu.org/software/libc/manual/html_node/File-Locks.html